Plasmapheresis decreases neuroelectric blocking activity in multiple sclerosis.

Serum neuroelectric blocking factor activity diminished after plasmapheresis in five of seven patients with MS but returned to baseline levels in 2 to 3 weeks. In the other two patients changes were insignificant. All patients studied had progressing symptoms. Five plasma exchanges of 2 liters were performed in 10 days. Two patients improved clinically, whereas five did not. There was no correlation between the level of neuroelectric blocking activity and changes in clinical status.